Development of a Method for Measuring Carbon Balance in Chemical Sequestration of CO2

Cheng, Zhongxian ; Pan, Wei-Ping ; Riley, John T.

Dr. John T. Riley (Paras Research Corporation)

关键词: Carbon Dioxide, Distribution, Sequestration, Carbon 14;    Biomass;    Carbon Dioxide;    Magnesium Carbonates;    Power Generation;   

DOI  :  10.2172/891228
RP-ID  :  DOE/ER/83740
RP-ID  :  FG02-03ER83740
RP-ID  :  891228

美国|英语

来源: UNT Digital Library

【 摘 要 】

Anthropogenic CO2 released from fossil fuel combustion is a primary greenhouse gas which contributes to “global warming.” It is estimated that stationary power generation contributes over one-third of total CO2 emissions. Reducing CO2 in the atmosphere can be accomplished either by decreasing the rate at which CO2 is emitted into the atmosphere or by increasing the rate at which it is removed from it. Extensive research has been conducted on determining a fast and inexpensive method to sequester carbon dioxide. These methods can be classified into two categories, CO2 fixation by natural sink process for CO2, or direct CO2 sequestration by artificial processes. In direct sequestration, CO2 produced from sources such as coal-fired power plants, would be captured from the exhausted gases. CO2 from a combustion exhaust gas is absorbed with an aqueous ammonia solution through scrubbing. The captured CO2 is then used to synthesize ammonium bicarbonate (ABC or NH4HCO3), an economical source of nitrogen fertilizer. In this work, we studied the carbon distribution after fertilizer is synthesized from CO2. The synthesized fertilizer in laboratory is used as a “CO2 carrier” to “transport” CO2 from the atmosphere to crops. After biological assimilation and metabolism in crops treated with ABC, a considerable amount of the carbon source is absorbed by the plants with increased biomass production. The majority of the unused carbon source percolates into the soil as carbonates, such as calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). These carbonates are environmentally benign. As insoluble salts, they are found in normal rocks and can be stored safely and permanently in soil. This investigation mainly focuses on the carbon distribution after the synthesized fertilizer is applied to soil. Quantitative examination of carbon distribution in an ecosystem is a challenging task since the carbon in the soil may come from various sources. Therefore synthesized 14C tagged NH4HCO3 (ABC) was used. Products of ammonium bicarbonate (ABC) or long-term effect ammonium bicarbonate (LEABC) were tagged with 14C when they were synthesized in the laboratory. An indoor greenhouse was built and wheat was chosen as the plant to study in this ecosystem. The investigated ecosystem consists of plant (wheat), soils with three different pH values (alkaline, neutral and acid), and three types of underground water (different Ca2+ and Mg2+ concentrations). After biological assimilation and metabolism in wheat receiving ABC or LEABC, it was found that a considerable amount (up to 10%) of the carbon source is absorbed by the wheat with increased biomass production. The majority of the unused carbon source (up to 76%) percolated into the soil as carbonates, such as environmentally benign calcium carbonate (CaCO3). Generally speaking, alkaline soil has a higher capability to capture and store carbon. For the same soil, there is no apparent difference in carbon capturing capability between ABC fertilizer and LEABC fertilizer. These findings answer the question how carbon is distributed after synthesized fertilizer is applied into the ecosystem. In addition, a separate post-experiment on fertilizer carbon forms that exist in the soil was made. It was found that the up to 88% of the trapped carbon exists in the form of insoluble salts (i.e., CaCO3) in alkaline soils. This indicates that alkaline soil has a greater potential for storing carbon after the use of the synthesized fertilizer from exhausted CO2.